Comet

Definition

A comet is a small celestial body composed primarily of ice, dust, and rocky material that orbits the Sun. When close to the Sun, it displays a visible atmosphere or coma and sometimes a tail.

5 Must Know Facts For Your Next Test

1. Comets are often described as 'dirty snowballs' due to their composition.
2. The two main parts of a comet are the nucleus and the coma.
3. Comet tails always point away from the Sun due to solar wind and radiation pressure.
4. Comets originate from two main regions: the Kuiper Belt and the Oort Cloud.
5. The periodicity of comets can vary, with some having short periods (less than 200 years) while others have long periods (more than 200 years).

Review Questions

• What causes a comet's tail to form and in what direction does it point?
• Name the two primary regions in our solar system where comets originate.
• Describe the main components that make up a comet.

Related terms

Asteroid: A small rocky body that orbits the Sun, mostly found in the asteroid belt between Mars and Jupiter.

Kuiper Belt: A region beyond Neptune filled with icy bodies, considered a source of short-period comets.

Oort Cloud: A distant spherical shell of icy objects surrounding our solar system, thought to be a source of long-period comets.